Process for the manufacture of phenyl and substituted phenyl acrylates and their polymers



Patented July 1, 1947 sr'r PROCESS FOR PHE THE MANUFACTURE OF NYL AND SUBSTITUTED PHENYL AC- RYLATES AND 'rnnm POLYMERS Edward M. Filachione, Philadelphia, and Charles H. Fisher, Abington, Pa., asslgnors to United States of America, as represented retary of Agriculture by the See- No Drawing. Application December 10, 1943,-

Serial No. 513,742

, 4 Claims. (01.260- 179) (Granted under the act of March 3, 1883, as

This application is made under the act of March 3, 1883, as amended by the act of April 30, 1928, and the invention herein described, if patented, may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment to us of any royalty thereon.

This invention relates to the the preparation of phenyl and substituted phenyl acrylates and polymers and interpolymers thereof.

An object of our invention is the preparation oi? aryl and substituted aryl acrylates, such as phenyl or tolyl acrylate of relatively high molecular weight and low vapor pressure, some of which are hitherto unknown polymerizable compounds.

A further object is the provision of a new and advantageous method of preparing phenyl and substituted phenyl acrylates.

Polymers and copolymers of phenyl and substituted phenyl acrylates have in a controllable degree the properties of fluidity, elasticity, plasticity, tensile strength, electrical resistance, resistance to water, organic liquids and gases, transparency, and so forth, which are properties highly desirable in the group of substancescommonly designated as plastics. Also, the phenyl and substituted phenyl acrylates are particularly valuable in that they can be used with other unsaturated monomers to prepare copolymers having various desirable properties.

It is known that unsaturated hydrocarbons may be produced by the elimination of acetic acid from the acetylated alcohol. For example, 2,4-dimethyl pentene-2 is produced by the pyrolysis of acetylated 2,4-dimethyl pentanol-3 (Van Pelt and Wibaut, Rec. tray. chim. 57, 1055 (1938), 60, 55 -64 (1941): Stevens and Richmond, J. Am. Chem. Soc. 63. 3132-6 (1941) It is also known that unsaturated acids may be formed by the pyrolysis of the acetylated derivatives of polycarboxylic acids. For example, aconitic ester is produced by pyrolysis of the acetylated citric ester. and maleic anhydrlde is produced by the pyrolysis of acetylated malic anhydride. (Hurd, "Pyrolysis of Carbon Compounds, A. C. 8. Mon-- o raph 50, New York, Reinhold Publishing Corp. 1929). Further. it is known that the acetylated' methyl ester of lactic acid on pyrolysis produces methyl acrylate, but the ethyl ester and higher amended April 30, 1928; 370 O. G. 757) 1940; U. S. 2,229,997, Jan. 28, 1941). This tendency increases as the molecular weight of the alkyl group increases. Thus, the preparation of acrylic esters by the pyrolysis of lactic esters has been limited, and in most instances it has not been feasible to make acrylic esters of high molecular weight in this manner.

We have found that the presence of a phenyl or substituted phenyl group in place of the alkyl group in the acetyl lactic ester (as shown below) CI-Ia.CI-I(OCOCH:) .coocsmn (where R is hydrogen or an alkyl radical) decreases the undesirable side reactions encountered in pyrolysis of the alkyl alpha-acetoxypropionates of higher molecular weight, and that, owing to the unusual stability of the phenyl and substituted phenyl radicals and their esters, their alpha-acetoxypropionates can be converted readily and in high yields into the phenyl and substituted phenyl acrylates, as shown below:

' Pyrolysis CH:.CH(OCO QH;).COO.A1- CHnCBLCOOAr (Aryl alpha-acetoxypropionate) (Aryl acrylate) temperatures above 600 C. excessive decomposi- V tion into undesired by-products occurs. Although the examples given below mention only the acetyl derivatives of phenyl and substituted.

phenyl lactates, other similar derivatives, such as the propionyl and benzoylderivatives (propionates, benzoates), may also be used.

By way of illustration, our process comprises: (1) The conversion of lactic acid into alphaacetoxypropionlc acid; alpha-acetoxypropionyl chloride, or alpha-'acetoxypropionic accordance with the reactions:

anhydride in (Al ba-acetoxypropionyl p chloride) (c) cmomooocmmooa 011.:

' (Alpha-aoetoxypropionic Ketene acid) icmomooocmyco o (Alpha-acetoxypropionio anhydride) (2) The preparation of aryl alpha-acetoxypropionate by reaction of alpha-acetoxypropionyl chloride or alpha-acetoiwpropionic anhydride withaphenol:

(a) CH .CH(OCOCH;).COC1 ArOH CHi.CH(OCOCHa).COO.Ar 1101 (o) lcmcmocoomycopo ArOH CH;.CH(OCOCH:).COO.A1 cmcmococnncoon or by ester interchange between alpha-acetoxy-- propionic acid and an aryl ester, such as the acetates. of the phenols:

(c) CI-Ia.CH(OCOCH3).COOH+RCOOAr- CH3.CH(OCOCH3) .COO.AI+RCOOH where R is hydrogen or an alkyl radical and Ar is an aryl radical.

(3) The conversion of phenyl or substituted phenyl alpha-acetoxypropionate into phenyl or substituted phenyl acrylate and acetic acid by means of pyrolytic decomposition, in accordance with the reaction:

CH3.CH(OCOCH3) .COO.Ar-

CH2 2 CH.COO.A1'+CH3COOH tioned above and their polymers:

Example I Phenyl alpha-acetoxypropionate (116 g.), prepared according to the methods described above, was allowed to run at an approximate rate of 3.2 cc. per minute (contact time approximately 11 seconds) into a Pyrex tube 30 mm. internal diameter and heated over a length of 13 inches. The tube was heated by an electric furnace and the temperature was controlled automatically. The average temperature was 532C. The apparatus was swept out with nitrogen before the pyrolysis was started and also after all of the liquid had been added. A small amount of hydroquinone was added to the condensate to prevent premature polymerization. The crude pyrolysis product consisted of 110 g., which by titration was shown tocontain 0.29 mole of acetic acid. The crude pyrolysis product was then distilled at a pressure of approximately mm. 0! mercury.

4 An approximately 3 percent yield of styrene was isolated from the acetic acid fraction. The phenyl acrylate (34.8 g.), which was collected at 83 to 93 C. at 9-11 mm., was yellow or amber. Some of the starting material (51.8 g. of phenyl alpha-acetoxypropionate) was also recovered boiling at 135 to 142 C. at 11 mm. The yield of phenyl acrylate based on the 64 g. of starting material destroyed was 76 percent of the theoretical, the yield of acetic acid was 94 percent. The gaseous products of pyrolysis were principally carbon monoxide and carbon dioxide.

A purified sample of phenyl acrylate was'found to boil at 64 to 65 C. at 2 mm., and to have a refractive index (D line) of 1.5216 at 20 C., and

I a density of 1.0762 at 20 C.

Example II o-Tolyl alpha-acetoxypropionate, prepared according to the methods described above, was pyrolyzed in essentially the same equipment as described in Example I. When 49.4 g. of o-tolyl alpha-acetoxypropionate was pyrolyzed in a tube. packed with Pyrex glass, at 500 C. at an average rate of approximately 15 drops per minute (contact time approximately 15 seconds), there was obtained 46.7 g. of liquid products. Distillation of the pyrolysis product gave 15.7 g. of o-tolyl acrylate boiling at 58 to 64 C. at approximately 0.5 mm, and 19.4 g. of unchanged starting material. The yield of o-tolyl acrylate based on the o-tolyl alpha-acetoxypropionate decomposed was 72 percent. 7

A purified sample of o-tolyl acrylate was found to boil at 58 to 59 C. at 0.5 mm., and to have an index (11 at 20 C.) of 1.5160. The density at 20 C. was 1.050.

. Example III Phenyl acrylate obtained by distillation of the pyrolysis product of phenyl alpha-acetoxypropionate apparently contains small amounts of an inhibitor and when a sample of this phenyl acrylate was heated with l'percent by weight of benzoyl peroxide at 75 C. did not show any signs of polymerizing. However, when the phenyl acrylate is washed with cold dilute alkali (5 percent sodium hydroxide), the inhibitor is eflectively removed. Thus, a sample of phenyl acrylate, which had been purified by washing with cold dilute sodiumhydroxide, when heated with 1 percent of its weight of benzoyl peroxide at 75 C., changed to a soft polymer after 15 minutes. After heating overnight the polymer was soft at C. but hard at room temperature.

Example IV Example V Phenyl alpha-acetoxypropionate was pyrolyzed in essentially the same equipment as described in Example I with the modification that the pyrolysis tube was operated under a pressure of 18-19 mm. of mercury and the feed was vaporized in a preheater at 220 C. prior to introduction into the a. Altai. ia-MWWM furnace. Thus, at 541 C. when the phenyl alphaacetoxypropionate (78.9 g.) was added over a period of 2.5 hours (contact time 0.77 second),

there was obtained 78.3 g. (99.5 percent recovery) The yield of phenyl acrylate, based on the phenyl alpha-acetozqrpropionate decomposed, was 80 per- 9 cent.

It will be apparent to those skilled in the art that various modifications may be employed in carrying out our invention. For example, lactic acid may be converted into alpha-acetoxypropicnic acid by treatment with acetyl chloride, ketene or acetic anhydrlde. Moreover, alphaacetoxypropionic acid may be converted into the corresponding acid chloride by treatment with various reagents, such as phosphorous chlorides or thionyl chloride. Ketene or acid anhydrides, such as acetic anhydride, may be used to convert'alphaacetoxypropionic acid into alpha-acetoxypropionic anhydride, or alpha-acetoxypropionic acetic anhydride; either anhydride may be treated with phenol or a substituted phenol to form the corresponding phenyl ester. Moreover, beta-hydroxyp propionic acid and its derivatives may be used by the methods of our invention to make-various aryl acrylates.

Having thus described our invention, we claim:

'1. The process of preparing aryl acrylates which. comprises pyrolyzing the correspondingaryl ester of alpha-acetoxypropionic acid at a temperature of about 400 to 600 C. for such time as required to produce the desired aryl acrylate.

2. The process of preparing phenyl acrylate which comprises pyrolyzing phenyl alpha-acetoxypropionate at a temperature of about 400 to .600 C. for such time as required to produce the phenyl acrylate.

3. The process of preparing ortho-tolyl acrylate which comprises pyrolyzing ortho-tolyl alphaacetgxypropionate at a temperature of about 400 to 6 0 C.

4. Ortho-tolyl acrylate, represented by the for- The following references'are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,183,357 Ritchie et a1. Dec. 12, 1939 2,200,709 Trommsdorff May 14, 1940 OTHER REFERENCES Du Pont, article in Ind. Eng. Chem., vol. 28, pp. 1160-1163 (1936).

Burns et al., article in Jour. Chem. Soc. (Lon- VJ don), 1935, pp. 400-406, 260-486.

C. Hurd, Pyrolysis of Carbon Compounds, p. 532, pub. by- Chemical Catalog 00., N. Y., 1929. 

